Carburetor metering valve screws



Dec. 17,195?

A. G. KADDIS ETAL CARBURETOR METERING VALVE SCREWS M 2 w 8 m M m INVENTDRE ALBER B. KAIIDIS ATT URNEY United States Patent CARBURETOR METERING VALVE SCREWS Albert G. Kaddis and Ralph A. Shade, Rochester, N. Y.

Application September 18, 1953, Serial No. 380,894

2 Claims. (Cl. 137-550) This invention relates to carburetor metering valve screws, and more particularly to such screws providing an air bleed, and the provision of a filter screen therefor.

In internal combustion engine carburetors, particularly as applied to automotive vehicles, it is desirable to admit auxiliary air to the idling fuel prior to introducing such fuel into the carburetor throat. Such air admission assists in providing improved mixing, and tends to lean a mixture often too rich. Further, the admission of auxiliary air in such manner improves economy by reducing the flow of idling fuel, when the engine is acting as a brake, or decelerating.

The present invention is directed toward providing a unitary metering screw having an air bleed, with a filtering screen to prevent the entrance of foreign matter, and to prevent clogging of the air bleed passage. The structure is unitary, capable of adjustment without disturbing the filtering effect of the screen, so that adjustment may be made under actual running conditions. The invention is further directed to an economical method of forming the parts from simple operations, which parts when assembled, form a permanent unitary metering screw and filter.

The above and other novel features of the invention will appear more fully hereinafter from the following detailed description when taken in conjunction with the accompanying drawings. It is expressly understood that the drawings are employed for purposes of illustration only and are not designed as a definition of the limits of the invention, reference being had for this purpose to the appended claims.

In the drawings, wherein like reference characters indicate like parts:

Figure 1 is an enlarged view of the idling screw (about 4 times);

Figure 2 is an axial sectional view taken substantially on the line 2-2 of Figure 1;

Figure 3 is an exploded perspective view showing the parts prior to assembly; and

Figure 4 is a fragmentary sectional view diagrammatically showing the relation of the screw to the idling port or jet of a form of carburetor.

Referring to the drawings, there is shown an idling adjustment screw for a carburetor, such screw acting as a control for the flow of fuel to the idling jet. In Figure 4, there is shown the throat of a down draft carburetor, such throat having a venturi 12, and throttle valve 14. Adjacent one edge of the throttle valve, when in substantially closed position, is an idling port or jet 16, communicating with a fuel supply channel 18, there also being provided an auxiliary port 20, located in advance of the port 16. The port 16 has an annular valve seat 22, adapted to cooperate with the tapered metering end 24 of the adjustable control or needle valve screw 26, to regulate the rate of flow.

The valve screw itself has a body portion 28, threaded as at 30, so as to be threadedly received in the carburetor Wall 32, such body portion being integral with the tapered metering end 24. In order to bleed air into the fuel being drawn into the carburetor throat below the throttle valve, the body portion of the metering screw has an axial bore 34, which may be reduced in diameter as at 36 before entering the metering end portion 24, in which portion such bore terminates, with a transverse radial or diametrical bore 38.

The outer end of the body portion has a substantially cylindrical exterior 40, which may have elementally extending knurling 42. The end terminates with a transverse planar surface 44. A cap member 46 having external knurling 48, and an internal bore 50 forming a skirt portion 51, is forced over the end of the body portion to form a permanent fit. The end or head 52 of the cap is provided with an axial bore 54, aligned with the bore 34 of the body portion, and a screw driver slot 56 is milled in the end diametrically thereacross.

In order to protect the bore from clogging as by the entrance of foreign matter or particles, a fine mesh screen 55 of bronze or other suitable material is interposed between the end 44 of the body or shank portion, and the inside surface 57 of the cap end. Such disk may have a mesh of to fine wires to the inch, and will be in effect clamped in the position shown in Figure 2, when the cap is forced upon the end of the shank. Such screen is readily observable through the bore 54 of the cap, and may be cleaned by blowing out the shank bore 34 or by reverse flow of cleaning fluid through the shank. The mesh of the screen affords adequate free flow of air into the bleed passages while protecting such passages from the entrance of foreign matter.

In practice, it will be understood that the heavy suction in the carburetor below the throttle valve, which is substantially closed during idling, will draw gasoline or other fuel from the port 16, as regulated by the tapered needle valve. The suction created will at the same time, draw air in through the axial and radial bores of the screw and lean the mixture, which in many cases would otherwise be too rich. Such air will create turbulence and aeration, and provide better mixing and improved idling performance. When the throttle is closed, and the motor is acting as a brake, the engine manifold suction on the port is increased, and fuel drawn into the engine is wasted. During such times, the air bleed acts to lessen the quantity of fuel drawn into the engine and thereby provides economy.

It will be seen that the screw as described is capable of manual adjustment without interfering with the air inlet, through thumb and finger engagement with the knurling 48. Further, if adjustment is to be made by a screw driver, the curvature 6%! of the milled slot prevents the blade of the screw driver from blocking the port to such an extent as to disturb the free fiow of air. Thus, adjustment is effected either manually or by a screw driver while the rigid assembly is functioning in its normal manner.

While a single embodiment of the invention has been illustrated and described, it is to be understood that the invention is not limited thereto. As various changes in the construction and arrangement may be made without departing from the spirit of the invention, as will be apparent to those skilled in the art, reference will be had to the appended claims for a definition of the limits of the invention.

What is claimed is:

l. A carburetor air bleed needle valve comprising a shank member having at one end a tapered needle valve portion, and one the other end a substantially cylindrical surface terminating abruptly and transversely of the shank axis to form a head end for receiving a cap, and an intermediate body portion between the needle valve portion and the cylindrical surface having screw threads along the length thereof, said shank having an axial bore extending from the head end to a point adjacent the intermediate portion end of said needle valve portion, said shank having a transverse bore through the needle valve portion communicating with the said axial bore, a hollow cap having a head and a substantially cylindrical skirt of an internal diameter for a press fit over the shank cylindrical surface, said cap being permanently positioned upon said shank, and having an axial bore in the head thereof in alignment with said shank bore, and a fine mesh screen disk filter element held and clamped upon the head end of the shank member by the hollow cap and extending transversely across the end'of said axial shank bore, said head having a diametral slot extending across the head and said slot having a concave bottom.

2. A carburetor air bleed needle valve comprising a shank member having at one end a tapered needle valve portion, and on the other end a substantially cylindrical surface terminating abruptly and transversely of the shank axis to form a head end for receiving a cap, and an inl termediate body portion between the needle valve portion and the cylindrical surface having screw threads along the length thereof, said shank having an axial bore extending from the head end to a point adjacent the intermediate portion end of said needle valve portion, said shank having a transverse bore through the needle valve portion communicating with the said axial bore, a hollow cap having a head, and a substantially cylindrical skirt, the exterior thereof being knurled, and the interior thereof being of an internal diameter for a press fit over the shank cylindrical surface, said shank adjacent the head end being knurled lengthwise to grip the cap, said cap being permanently positioned upon the knurled portion of said shank, and having an axial bore in the head thereof in alignment with said shank bore, and a disk filter element held and clamped upon the head end of the shank member by the hollow cap and extending transversely across the end of said axial shank bore, said head having a diametral slot extending across the head and said slot having a concave bottom.

References Cited in the file of this patent UNITED STATES PATENTS Featherston Feb. 22, 

